• Title/Summary/Keyword: internal flows

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Numerical Analysis of Three Dimensional Supersonic Flow around Cavities

  • Woo Chel-Hun;Kim Jae-Soo;Kim Jong-Rok
    • 한국전산유체공학회:학술대회논문집
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    • 2006.05a
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    • pp.311-314
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    • 2006
  • The supersonic flow around tandem cavities was investigated by three- dimensional numerical simulations using the Reynolds-Averaged Navier-Stokes(RANS) equation with the $\kappa-\omega$ thrbulence model. The flow around a cavity is characterized as unsteady flow because of the formation and dissipation of vortices due to the interaction between the freestream shear layer and cavity internal flow, the generation of shock and expansion waves, and the acoustic effect transmitted from wake flow to upstream. The upwind TVD scheme based on the flux vector split using van Leer's limiter was used as the numerical method. Numerical calculations were performed by the parallel processing with time discretizations carried out by the 4th-order Runge-Kutta method. The aspect ratio of cavities are 3 for the first cavity and 1 for the second cavity. The ratio of cavity interval to depth is 1. The ratio of cavity width to depth is 1 in the case of three dimensional flow. The Mach number and the Reynolds number were 1.5 and $4.5{\times}10^5$, respectively. The characteristics of the dominant frequency between two-dimensional and three-dimensional flows were compared, and the characteristics of the second cavity flow due to the fire cavity flow cavity flow was analyzed. Both two dimensional and three dimensional flow oscillations were in the 'shear layer mode', which is based on the feedback mechanism of Rossiter's formula. However, three dimensional flow was much less turbulent than two dimensional flow, depending on whether it could inflow and outflow laterally. The dominant frequencies of the two dimensional flow and three dimensional flows coincided with Rossiter's 2nd mode frequency. The another dominant frequency of the three dimensional flow corresponded to Rossiter's 1st mode frequency.

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A Preliminary Trophic Flow Model for Gwangyang Bay, Korea (광양만 예비 영양류 모형)

  • Kang, Yun-Ho
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.38 no.3
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    • pp.184-195
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    • 2005
  • A preliminary quantitative model of the trophic structure in Gwangyang bay, Korea was obtained using ECOPATH and data from relevant studies to date in the region. The model integrates and analyzes biomass, food spectrum, trophic interactions and the key trophic pathways of the system. The bay model comprises 9 groups of benthic primary producer, phytoplankton, zooplankton, benthos, bivalve, pelagic fish, demersal fish and piscivorous fish. The total system throughput was estimated at $2.4\;kgWW/m^2/yr$, including a consumption of $41\%$, exports of $9\%$, respiratory flows of $24\%$ and flows into detritus of $26\%$. All of which originate from primary producers measured at $52\%$ and detritus of $48\%$. The total biomass was seen to be high compared to the levels of Somme, Delaware, Chesapeake Bays and Seine Estuary. This seems to be possibly due to artificial bivalve aquaculture and overestimation of benthos and benthic primary producer groups. The deviation can be calibrated by neglecting aquaculture and decreasing the habitat area for the groups. The trophic network of the bay shows a low level of recycling and organization as indicated by Finn's cycling index $3.3\%$, Ascendancy $3.1\;kgC/m^2/yr$ bits, Capacity $5.1\;kgC/m^2/yr$ bits and Redundancy $2.2\;kgC/m^2/yr$ bits. A high relative ascendancy of $62\%$ and a low internal relative ascendancy of $18\%$ indicate the system is not fully organized and stable towards disturbances, depending upon external connections. Although the model should be continuously provided with field data and calibrated further in depth, this study is the first trophic model applied to the region. The model can be a useful tool to understand the ecosystem in a quantitative manner.

Estimation of background minimum night flows by metering water use in water distribution areas (야간사용량 측정을 통한 배급수구역 배경야간최소유량 산정)

  • Lee, Doo-Jin;Kim, Do-Hwan;Kim, Ju-Hwan;Kim, Kyoung-Pil
    • Journal of Korean Society of Water and Wastewater
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    • v.24 no.5
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    • pp.495-508
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    • 2010
  • The aim of this study is to develop a quantified water loss Index to evaluate and manage leakage scientifically for the reduction of non-revenue water in water distribution systems. For the purpose, unavoidable background leakage suggested from UK water industry and IWA, and allowable water leakage in accord with the concept of allowable water loss are proposed by analyzing the inflow into two study water districts and the short-term water use of each customer in the districts. The study distribution areas are selected among the metered districts with good maintenance of leakage after improvement activities in Nonsan, medium sized city in Korea. Estimation models of allowable leakage are developed by metering and analyzing the minimum night flow at residential and commercial areas in the city. In the results of the investigation, it is estimated that background night flow in residential area was larger than that of commercial area where the types of business shows small water use characteristics. Meanwhile, night flow and background water loss on internal plumbing systems show great differences for each district which is influenced much by the water use characteristics and facilities scale. Based on metering water use data in various districts, leakage management criteria can be established under the consideration of domestic conditions in Korea by analyzing separated real water use and background leakage and it is possible to apply into presentation of optimal leakage level and reasonable time for working activities for leakage reduction.

Two Layer Modelling with Applications to Exchange Flow and Internal Tide (이층류 모델링의 교환류와 내부조석파 연구에의 적용)

  • Kang, Sok-Kuh;Abbott, Michael-B.;Heung, Jae-Lie;Yum, Ki-Dai
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.9 no.1
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    • pp.9-23
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    • 1997
  • A numerical study of a two-layer, stratified flow is investigated, using the implicit finite difference method in one dimension. The results of computational method have been tested and, in case of lock exchange flow, compared with the results of experimental data. The results of model experiments with various interfacial, bottom friction coefficients along with various time weighting factor of numerical scheme and dissipative interface are shown and discussed. Two-layer model experiment has been also carried out to investigate the generation and propagation characteristics of internal tidal wave over the steep bottom topography under stratified condition. The internal wave seems to well radiate through the downstream boundary under the experiments adopting radiation conditions both at two layers and only at upper layer, confirming the applicability of radiational boundary condition in stratified flows. It is also shown that the internal wave through the downstream boundary propagates more actively with increasing thickness of lower layer in the downstream. This implies that the potential tidal energy in the interface will depend upon the thickness of lower layer for the constant thickness of upper layer.

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Relationship between Net working capital and Cash flows in General Hospitals, Hospitals (병원의 현금흐름 종류가 순운전자본에 미치는 영향)

  • Jung, Yong-Mo;Ha, Au-Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.6
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    • pp.312-318
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    • 2017
  • This study calculated the cash flow using the financial information by fiscal year for 25 general hospitals and 23 hospitals, and analyzed the relationship between cash flow and net working capital. The analysis results showed that 73.3% of general hospitals and 83.3% of hospitals did not secure funds required for operating activities by fiscal year. The cash flow types that affect net working capital were expenses not involving cash outflows and changes in borrowings in general hospitals, and expenses not involving cash outflows and income not involving cash inflows and changes in borrowings in hospitals. However, in case of shortage of funds required for operating activities, at general hospital, due to expenses not involving cash outflows being high and income not involving cash inflows being low and resulting in increased borrowing, at hospital, due to expenses not involving cash outflows being high and resulting in increased borrowing. Therefore, for the stability of cash flow in management activities, the adequacy and relevance of the expenses not involving cash outflows need to be reviewed, and it will be necessary to review the appropriate internal policy measures to systematically and rationally manage cash flow in consideration of cash flows.

Free Flow in Internal Thoracic Artery and Internal Thoracic Artery-Radial Artery Composite Graft (속가슴동맥 편 및 속가슴동맥-노동맥 복합이식편의 자유혈류)

  • 고광표;이미경;류대웅;이삼윤;최종범
    • Journal of Chest Surgery
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    • v.37 no.10
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    • pp.839-844
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    • 2004
  • Background: The Y-composite graft of internal thoracic artery and radial artery is commonly used in coronary bypass surgery. The aim of this study is to look for a way to raise the free flow of the internal thoracic graft and to see flow dynamics of the Y-graft. Material and Method: In 15 patients undergoing coronary bypass surgery, free flow of the in-situ internal thoracic artery graft was measured using two different papaverine application methods; extraluminal papaverine spray in 7 patients and intraluminal papaverine injection in 8. In 18 other patients for whom the Y-graft was used, total free flow and flow changes from the two ends were measured. Result: The free flow of the in-situ internal thoracic artery graft almost doubled with internal papaverine injection than with external papaverine spray $(47.7\pm9.6$ mL/min $vs.100.8\pm26.3$ mL/min, p<0.001). Total flow of the Y-composite graft was significantly more than either flow of the internal thoracic artery end or radial artery graft end $(173.3\pm45.3$ mL/min vs. $121.1\pm34.3$ mL/min or $117.5\pm42.8$ mL/min). When both ends of the Y-composite graft were opened, free flows from the two ends were similar $(85.4\pm27.8$ mL/min vs: $87.9\pm42.4$ mL/min, p=0.772). The flow of one end of the Y-composite graft was increased significantly by clamping of the other-end than when both ends were opened. Conclusion: Intraluminal papaverine injection is very effective in raising free flow of the internal thoracic artery graft, and the free flow of the Y-composite graft of in-situ internal thoracic artery and free radial artery graft is more than that of the in-situ internal thoracic artery graft. The flow of one end flow of the Y-graft may be altered by the flow change of the other end.

A study on the relationship between the symptom of Shanghanlun(傷寒論) and the Nutritive-Gi(營氣) (『상한론(傷寒論)』 병증(病症)과 영기(營氣)의 관계에 대한 연구(硏究))

  • Bang, Jung-kyun
    • Journal of Korean Medical classics
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    • v.30 no.1
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    • pp.211-221
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    • 2017
  • Objectives : The practices of Wei-qi and Nutritive-qi are generally divided into external Mai and internal Mai. However, they are closely interrelated and practiced together. While taking these aspects into consideration, this paper attempts to make interpretations in relation with Nutritive-qi the disease pathogens that appear in Shanghanlun's disease symptoms. Methods : Using the practice and function of Nutritive-qi described in Huangdineijing, the paper shall make interpretations for the patterns of Mawhangtang, patterns of Gaejitang, and the pathologies of pain, oedema, and nosebleed as described in Shanghanlun. Results & Conclusions : The pain from the patterns of Gaejitang differ from that of the patterns of Mawhangtang. First, the pain from the the patterns of Gaejitang cannot be the main symptom. Even if there is a symptom of pain, it's severity is not serious. Second, the pain from the patterns of Gaejiang takes the form of stiffness, and not general bodily pain. The reason for this stiffness is because of the emptiness of Wei-qi that leads to the congestion of Nutritive-qi which in turn causes the lack of qi and blood flow in muscula area such as abdomins. The symptom of oedema where one's body becomes swollen comes from a number of pathogens. First, the flow of meridian becomes hindered due to external dampness, a character which tends to be adhesive when added with humidty, and this results in the blockage of water qi which then causes the coagulation of nutritive blood. Second, when toxic heat is repressed and blocked within the lesser-yang channel, lesser-yang meridian stops working, which causes nutritive blood to clog at the front and back of ears since lesser-yang channel flows through that portion of body. Third, although oedema is not specifically mentioned in the sentences, but there exists the patterns of Daechungyongtang where water lumps are formed due to the accumulation and blockage of watery dampness. The patterns of Daechungyongtang is cuased when meridian is hindered from externally discharging body fluid due to a problem with meridian that blocks the fumigated internal heat which turns into bodily fluid from being discharged externally.

Study on the Atomization Characteristics of a Counter-swirling Two-phase Atomizer with Variations of Swirl angle (역선회 이류체 미립화기의 선회각 변화에 따른 미립화 특성연구)

  • Kim, N.H.;Lee, S.G.;Ha, M.H.;Rho, B.J.;Kang, S.J.
    • Proceedings of the KSME Conference
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    • 2001.06e
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    • pp.125-130
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    • 2001
  • Experimental and analytical researches have been conducted on the twin-fluid atomizers for better droplet breakup during the past decades. But, the studies on the disintegration mechanism still present a great challenge to understand the drop behavior and breakup structure. In an effort to describe the aerodynamic behavior of the sprays issuing from the internal mixing counter-swirling nozzle, the spatial distribution of axial (U) radial (V) and tangential (W) components of droplet velocities are investigated across the radial distance at several axial locations of Z=30, 50, 80, 120 and 170mm, respectively. Experiments were conducted for the liquid flow rates which was kept constant at 7.95 g/s and the air injection pressures were varied from 20 kPa to 140 kPa. Counter-swirling internal mixing nozzles manufactured at angles of $15^{\circ},\;30^{\circ},\;45^{\circ}$ and $60^{\circ}$ the central axis with axi-symmetric tangential-drilled holes was considered. The distributions of velocities and turbulence intensities are comparatively analyzed. PDPA is installed to specify spray flows, which have been conducted along the axial downstream distance from the nozzle exit. Ten thousand of sampling data was collected at each point with time limits of 30 second. 3-D automatic traversing system is used to control the exact measurement. It is observed that the sprays with all swirl angle have the maximum SMD for on air injection pressure of 20 kPa and 140 kPa with centerline, respectively. The nozzle with swirl angle of $60^{\circ}$ has vest performance.

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The Effect of Seepage Forces on the Ground Reaction Curve of Tunnel (침투력이 터널의 지반반응곡선에 미치는 영향)

  • Lee Seok-Won;Jung Jong-Won;Nam Seok-Woo;Lee In-Mo
    • Journal of the Korean Geotechnical Society
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    • v.21 no.3
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    • pp.87-98
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    • 2005
  • When a tunnel is excavated below groundwater table, the groundwater flows into the excavated wall of tunnel and seepage forces are acting on the tunnel wall. The ground reaction curve is defined as the relationship between internal pressure and radial displacement of tunnel wall. Therefore, the ground reaction curve is significantly affected by seepage forces. In this study, the theoretical solutions of ground reaction curves were derived for both the dry condition and the seepage forces. The theoretical solutions derived were validated by numerical analysis. The ground reaction curves with the support characteristic curve were also analyzed in various conditions of groundwater table. Finally, the theoretical solutions of the ground reaction curve derived in this study can be utilized easily to determine the appropriate time of support systems, the stiffness of support system and so forth for the reasonable design.

An MVP-based XML Language for User Interfaces (사용자 인터페이스를 위한 MVP기반의 XML 언어)

  • 최종명;신경희;유재우
    • Journal of KIISE:Software and Applications
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    • v.29 no.12
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    • pp.947-956
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    • 2002
  • It is advantageous to use XML in developing user interfaces, since XML is independent from platforms and languages and it is easy to learn and use. The existing XML-based languages do not adopt formal model, and they are developed in ad hoc manner. Moreover, they provide limited facilities to handle user events, and combine user interface components with internal logics. In this paper, we introduce an extended MVP (EMVP) model, which is extended from MVP (Model-View-Presenter), and XUIML, which is a new XML application based on the EMVP to support user interface. XUIML provides useful methods to build user interface, including methods to describe actions on user events, data flows between objects, and internal logics. The XUIML system provides two style editors - text editor and graphic editor. It also provides two code generators. One generates Java source, and the other generate C# code from XUIML document. The XUIML graphic editor allows users to manipulate XML elements directly, and we can gain high productivity with the graphic editor.